Propellant composition comprising nitroparaffin gel



lt atenteel July 12, 1%55 PRDIELLANT COMPtlSlTEQN COllZPRISiNG NITRGPARAFFEN GEL Herman Maisner, Les Angeies, alif., assignor, by mesne assignments, to Aerojet-General (Iorporation, juicinnati, Ohio, a corporation of {Fabio No Drawing. Application February 1, 1947, Serial No. 725,977

3 Claims. (Cl. 52-il.5)

This invention relates to nitroparaffin-containing substances, and has for its principal object to provide a gel containing nitroparafiin, and a process of forming it.

Liquid nitroparailins have heretofore been employed as propellants in jet propulsion devices, and they have also been used in explosives. operating conditions to employ the liquid nitroparaifins in a solid or semi-solid form, or gel, for these purposes. Up to the present time, dihiculty has been encountered when it was attempted to produce gels from the various liquid nitroparafdns without seriously afiecting their oxygen balance and otherwise changing their properties.

By the present invention I have discovered a method for thickening, gelling, or solidifying liquid nitroparaffins and forming semi-solid or solid gels which retain their consistency for a period of time without undergoing any marked change.

This invention is, in general, directed to solidifying or gelling any of the liquid nitroparaflins including the mono, and poly nitromethanes, mononitroethane, mononitropropane, mononitroisopropane, mononitrobutanes, mononitroisobutanes, mononitropentanes and the like which are normally liquid compounds at room temperatures. Thus, I may employ any of the liquid nitroparaffins, such as mononitromethane (commonly called nitromethane, and so designated hereinafter), dinitromethane nitroethane, nitropropane, nitrobutane, and the like or any mixtures of the liquid nitroparaflins or solutions of any of the normally solid polynitroparafiins having sufficient oxygen to sustain self-combustion in nitromethane. Nitromethane is usually the preferred nitroparafiin for propellant and explosive purposes, in that it forms a very satisfactory self-con1bustible propellant when gelled with nitrocellulose and employed in the manner in which such propellants are usually used; and a very satisfactory explosive when gelled in combination with a sensitizer or otherwise treated and handled in the manner of an explosive.

I have discovered that it is possible to produce a homogeneous semi-solid or solid gel from liquid nitroparafiins by dissolving or adding to the liquid nitroparalfins, such as nitromethane, nitroethane and the like, a quantity of nitrocellulose. Various commercial forms in which nitrocellulose suitable for the purpose, may be obtained are: Pyrocellulose, pyroxylin, guncotton, etc., all of which are trade names for such nitrocelluloses.

The gelling of the nitroparaflins is preferably conducted at room temperatures, or temperatures not more than slightly above room temperatures, since both nitroparafiin and nitrocellulose become explosive when confined and subjected to more elevated pressures and temperatures. This is particularly true when a sensitizing agent has been added to nitromethane to assure its action as an explosive. At elevated temperatures, that is, above 350 F, nitromethane, for example, becomes extremely sensitive to shocks and at still higher temperatures may explode without subjecting the liquid to any shock whatsoever.

The gels produced from nitrocellulose and a liquid ni- It is desirable for some types of troparaifin may be compounded, by adjusting the proportions to give gels having varying degrees of viscosity. These range from syrupy materials to solid gels. For practical purposes the gels employed vary from between about 5% to nitrocellulose by weight based on the weight of nitroparaflin used. Gels may be made to contain any amount above 75% nitrocellulose by weight based on the weight of the total mixture but even 75% nitrocellulose gels are practically solid, there fore, there is little advantage from this standpoint in using a higher percentage of nitrocellulose.

Since nitroparaflins of the type of nitromethane, and nitrocellulose both have sufficient oxygen in their molecules to insure their complete combustion, these substances are capable of burning to completion at ambient conditions without requiring the addition of oxidizers. Gelled nitroparafiins such as nitromethane are particularly useful where it is desired to employ these substances as solid or semi-solid explosives or as self-combustible solid propellant fuels such as are used in self-contained rocket motors.

The nitroparaffin gels prepared according to my invention may be employed either as explosives or as self combustible propellants, depending upon the manner of use. The gels are explosive when detonated with sutficient force but may readily be adapted to be burned as fuels, particularly in jet propulsion motors, in the absence of detonation. if it is desired to prepare a nitroparaflin gel to be used as an explosive I may incorporate in the liquid nitroparatiin, prior to gelling a sensitizer. Such sensitizers as the organic amines disclosed by Laurence in patent application Ser. No. 695,747, filed July 18, 1945, are highly satisfactory, including the aromatic amines such as aniline, diphenylethylenediamine and the like and the allphatic amines such as diethylamine, tetraethylene pentamine and the like. A nitroparatfin gel in which a sensitizer suchas one of the organic amines is incorporated is much more sensitive to detonation than is the gel in the ZtUSfiI'lCG of the sensitizer, although it is to be understood that the use of a sensitizer is optional; and the gels may be employed as explosives either with or without a sensitizer.

Thus mixtures of nitromethane or other nitroparaffins and nitrocellulose containing from about 75% to about by weight of nitroparatiin based on the total weight may be satisfactorily used as explosives in conjunction with a suitable cletonator. Higher proportions of nitrocellulose may be employed; this tends to decrease the explosive strength.

Mixtures of nitroparafiin and nitrocellulose containing from 79% to 83% by weight of nitroparatlin such as nitromethane based on the total Weight of the mixture are easily exploded by the shock of a No. 8 fulminate type of blasting cap, yet in the absence of shock, such mixtures (containing as high as 74% to 84% by weight of nitromethane in combination with nitrocellulose) may be confined and burned satisfactorily as restricted propellant charges without exploding. A restricted propellant charge is defined as one in which the burning occurs over a predetermined face of limited area and does not take place simultaneously over the entire outside surface of the propellant mass. Restriction may be accomplished by coating all surfaces except the burning surface with a liner which is adhesive to the propellant sass and has a slower burning rate than the material forming the principal charge. Examples of adhesive liners suitable for confining the burning are ethylcellulose, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, etc.

The burning properties of solid propellant charges compounded by gelling nitromethane with nitrocellulose may be greatly improved by adding suitable catalysts to 3 the nitromethane before gelling. A particularly desirable catalyst for assisting the easy ignition of nitromethane is chrome acetyl acetonate. Small amounts of this substance ranging between a trace up to approximately 3% by weight may be used to improve the burning of nitromethane.

The ratio of nitroparatfin to nitrocellulose may, as stated, be varied over a wide range of proportions ranging from a trace of nitrocellulose in liquid nitroparafiin to a trace of nitroparaflin in nitrocellulose. The amount of nitrocellulose which may be incorporated into the liquid nitroparafiin by stirring or agitation alone will not appreciably exceed 45% based on the weight of the nitroparafiin employed.

A fairly substantial gel may be formed by dissolving in nitroparafnn as low as nitrocellulose by weight based on the weight of the nitroparafiin while a reasonably stilf gel is obtained when the amount of nitrocellulose employed is increased to or by weight based on the weight of the nitroparafiin employed. Particularly stiff gels are formed when to 50% by weight of nitrocellulose based on the weight of nitroparaflin present is employed.

If it is desired to incorporate amounts of nitrocellulose in excess of by weight, it is preferable to mill or knead the mixtures of nitrocellulose and a liquid nitroparaffin to insure a more homogeneous mixture.

The process herein described possesses the advantage that any desired consistency of gel may be easily produced from nitroparafiins. Sensitized nitroparaffins such as nitromethane may, by careful selection of the proportions of nitromethane to nitrocellulose, be used either as a solid or semi-solid explosive. Non-sensitized nitromethane and other self-combustible nitroparaffins may be made into self-combustible solid propellants. or may be used as explosives when detonated with sufiicient force.

The following examples of gels made according to invention serve to illustrate the application of the invention.

Example 1.--A gel consisting of 80% by weight of nitrornethane and 20% by weight of nitrocellulose has been prepared by dissolving the nitrocellulose in the nitromethane at 75 F. The gel thus formed was very stable and fairly rigid. Additional gels consisting of nitromethane and nitrocellulose were made in similar manner and contained nitrocellulose varying in proportions from about 10% to Example Z.Numerous other gels have been prepared by dissolving nitrocellulose in nitropropane and nitroethane at temperatures ranging from approximately F. to 90 F. These gels consisted of from about 50% to 90% by weight of the respective nitroparaflin and from about 10% to 50% by weight of nitrocellulose.

Example 3.A gel consisting of 14.6% by weight of nitrocellulose dissolved in 85.4% of nitrornethane formed a thick fluid gel.

Example 4.A gel consisting of 25% nitrocellulose and nitrornethane was prepared by dissolving the nitrocellulose in the nitromethane at approximately 75 F. This produced a fairly stifi gel.

Example 5.-A solution of 50% nitromethane into which has been dissolved 50% of nitrocellulose produced a very stiff gel having substantially solid properties.

Example 6.A sample of a gel consisting of 75.3% nitromethane which had dissolved therein 22.9% nitrocellulose was made more active by the addition of 1.8% of chrome acetyl acetonate. This formed a fairly stiff gel having suitable burning properties for a restricted propellant charge.

Example 7.-29.8% of nitrocellulose was dissolved in 69.2% of nitromethane and 1.0% of chrome acetyl acetonate was added to the mixture. This formed a stiff gel which appears to be very satisfactory when employed as a solid propellant charge.

Other gels which may be satisfactorily formed due to Lil the fact that nitrocellulose is a good gelling agent for nitromethane and similar nitroparamns are those which are made from solutions of solid organic polynitrocompounds in nitromethane. Examples of these substances are trinitrotoluene, polynitrobenzene, dinitropropane, dinitroethane and other higher polynitroparafi'lns which possess sufiicient oxygen in their molecules to sustain their self-combustion. These are selected to produce propellants having the required properties such as hardness, temperature coeificient and freedom from detonation.

An additional advantage of my process apparent from the foregoing examples, is that the ingredients may be compounded at ambient temperatures and require little or no heating, thus eliminating the hazard present when propellants are subjected to temperatures greatly in excess of ambient. This is particularly desirable in view of the fact that nitro-parafiins, such as nitromethane, become more 567 ive to shocks at elevated temperatures.

A particularly desirable feature, inherent in restricted burning propellant charges formed from solid gels of the above ingredients, is that the gases produced when these charges are burned in a jet motor are substantially smokeless, noncorrosive and nontoxic. The specific impulse obtained by burning nitromethane, or any other of the nitroparatlins having sufiicient oxygen in the molecule to support. their own combustion, in combination with nitrocellulose is not appreciably lower than that developed by the nitroparafiin alone.

Gels compounded from sensitized nitromethane and nitrocellulose may be formed into sticks similar to dynamite and may be substituted for dynamite since sensitized nitromethane when exploded compares favorably with nitroglycerin shattering properties and power. The addition of nitrocellulose does not appear to affect the ease with which sensitized nitromethane can be exploded when subjected to shocks.

1 claim:

1. A composition of matter comprising from about 10% to 50% by weight of nitrocellulose, 50% to 90% by weight of nitromethane, and from a trace to 3% by weight of chrome acetyl acetonate.

2. A composition of matter consisting of a mixture of a nitroparatlin, nitrocellulose and an ignition assisting catalyst comprising chrome acetyl acetonate, the weight or the nitroparaffin being between 50% and by weight based on the weight of the total mixture, and the weight of the nitrocellulose being between 15% and 50% by weight based on the weight of the total mixture.

3. A composition of matter consisting of a nitromethane, nitrocellulose and an ignition assisting catalyst comprising chrome acetyl acctonate, the weight of the nitromethane being between 50% and 85% by weight based on the weight f the total mixture, and the weight of the nitrocellulose being between 15% and 50% by Weight based on the weight of the total mixture.

References Cited in the file of this patent UNITED STATES PATENTS 745,802 Edelenu Dec 1, 1903 778,788 Maxim Dec. 27, 1904 1,985,968 Wyler Jan. 1, 1935 2,325,064 Lawrence July 27, 1943 2,338,l20 Lawrence Jan. 4, 1944 2,388,846 H-echt Nov. 13, 1945 FOREIGN PATENTS 201,907 Germany Sept. 30, 1908 394,992 France Feb. 6, 1909 24,839 Great Britain of 1913 310,789 Germany Mar. 18, 1921 362,348 Germany Oct. 26, 1922 111,963 Australia Nov. 28. 1940 OTHER REFERENCES Chemical industries, article by Scheer, April 1943,

page 473. (Copy in 260/324.) 

1. A COMPOSITON OF MATTER COMPRISING FROM ABOUT 10% TO 50% BY WEIGHT OF NITROCELLULOSE, 50% TO 90% BY WEIGHT OF NITROMETHANE, AND FROM A TRACE TO 3% BY WEIGHT OF CHROME ACETYL ACETONATE. 